Two putative protein kinase CK2 phosphorylation sites are important for Myf-5 activity.
Myf-5, a member of a family of muscle-specific transcription factors, is important for myogenic cell determination and differentiation. Here, we report that Myf-5 protein constitutes a substrate for phosphorylation in vitro by protein kinase CK2. We identified two potential phosphorylation sites at serine49 and serine133, both of which seem to be necessary for Myf-5 activity. Mutants which can no longer be phosphorylated fail to transactivate E-box-dependent reporter genes and act as trans-dominant repressors of wild-type Myf-5. Normal activity can be restored by replacing the serine residues with glutamate suggesting that a negative charge at these sites is obligatory for Myf-5 activity. Although serine133 is part of helix 2 which mediates dimerization, we find no evidence for impaired DNA-binding or heterodimerization of the Ser-Ala133 mutant. Some serine49 mutations exhibit reduced nuclear localization and/or protein stability. Our data suggest that CK2-mediated phosphorylation of Myf-5 is required for Myf-5 activity.
Winter
B
B
Department of Cell and Molecular Biology, University of Braunschweig, Germany.
Kautzner
I
I
Issinger
O G
OG
Arnold
H H
HH
D000818:Animals; D001665:Binding Sites; D047390:Casein Kinase II; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D051787:Myogenic Regulatory Factor 5; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012694:Serine / Q000235:genetics / Q000378:metabolism*; D015534:Trans-Activators; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
D004268:DNA-Binding Proteins; C497417:MYF5 protein, human; D009124:Muscle Proteins; D051787:Myogenic Regulatory Factor 5; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D012694:Serine; D004247:DNA; D047390:Casein Kinase II; D017346:Protein Serine-Threonine Kinases